A generic vibration exciter, as well as a ground compactor equipped therewith, are known, for example, from U.S. Pat. No. 7,059,802 B1. In order to improve the compacting action of the ground compactor shown, the compacting rollers are exposed to vibrations in compacting operation. The vibrations are generated by one (or by a plurality of) vibration exciters. A vibration exciter comprises an exciter shaft driven rotationally about an axis of rotation, on which a so-called exciter weight (exciter mass) is disposed eccentrically. In the following, “exciter weight” designates the structural entirety of exciter weight and exciter shaft unless otherwise specified. Vibrations which can be used for compaction are generated as a result of the imbalance produced by the eccentricity.
Furthermore, at least one so-called turnover weight which is also configured eccentrically (i.e., the center of mass lies outside the axis of rotation) is disposed on the exciter shaft. The turnover weight is rotationally decoupled with respect to the exciter shaft and the exciter weight located thereon or it can rotate about an axis of rotation and can adopt different angular positions with respect to the exciter weight in a rotational range delimited, for example, by stops. The axis of rotation of the exciter shaft with the exciter weight and the axis of rotation of the turnover weight relative to the exciter weight lie coaxially to one another.
The turnover weights are repeatedly entrained by the rotating exciter shaft by means of a pin (or the like) from a lower position as far as a kinematically determined turnover or rollover point at which the turnover weights roll over or turn over due to gravity and impact from the opposite side on a stop provided for this purpose on the exciter shaft or the exciter weight. The turnover weight can therefore, depending on the direction of rotation of the exciter shaft, adopt a position in which the mass of the turnover weight is added in the rotational movement to the exciter weight whereby the vibration amplitude is increased and another position in which the mass of the turnover weight acts against the mass of the exciter weight, whereby the vibration amplitude is reduced. The arrangement of exciter weight and turnover weight in the vibration exciter therefore allows the vibration intensity of the vibration exciter to be better regulated.
A disadvantage in the vibration exciters known from the prior art in particular is the uncontrolled recoil of the turnover weights upon impact. Another and frequently associated disadvantage is that frequently no distinct turnover of the turnover weight takes place. In practical operation it has further been shown that the turnover weight can adopt a neutral position in the known arrangements. As a result, for example, the position in which the turnover weight adds to the exciter weight cannot be reliably ensured or the maximum amplitude of the exciter unit cannot be achieved. As a result, the maximum compaction performance of the compactor cannot be provided.
It is the object of the present invention to further develop a vibration exciter of the relevant type in such a manner that the disadvantages associated with the prior art are obviated or at least significantly reduced.